The invention relates to bar code readers, and specifically to a hand held portable bar code reader of efficient and compact design.
Hand held bar code readers, employing scanned laser beams as an illuminating source for reading the bar codes, have come into wide use and have potentially many more uses. Conventionally, laser sources used for such portable bar code readers have included gas lasers such as helium-neon lasers, for example. However, these lasers are relatively large and cumbersome for use in a hand held laser, and a compact, lightweight, highly efficient laser diode would be much preferable for such applications.
There is a problem which is particularly acute with hand held bar code readers, and that is the problem of ambient light striking the bar code surface. Hand held readers are often used in bright ambient light, such as at loading docks where the sun might directly strike the bar code being read, essentially blinding the detectors of the bar code reader and preventing an accurate reading.
Conventionally, relatively expensive optical band pass filters have been used to alleviate this problem in bar code readers. These are generally effective, but their expense is an important practical consideration which may make a hand held reader too expensive to be feasible for may applications.
Another problem faced by hand held laser bar code scanners is that of restrictions from regulatory agencies on permissible beam output power. In some situations where hand held scanners are used, the distance to the bar code surface is relatively long, and for good readings this usually requires either a stronger laser beam, or the operator's moving closer to the bar code.
U.S. Pat. No. 4,387,297 discloses hand held laser bar code readers in several different embodiments. In columns 19 and 20 of that patent, there is briefly mentioned, in general terms, the provision of a hand held laser bar code reader incorporating a laser diode as the beam source, which may be of the continuous wave or pulse type.
It is an object of the present invention to provide an efficient, relatively low cost hand held bar code reader using a laser diode and being of efficient and economical construction, and with beam power sufficient to read bar codes at considerable distances while still remaining within regulatory limits, and including the capability of accurately reading a bar code in conditions of strong and viable ambient light.